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    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script>
        var a=100;
        var b=78;
        var c=a;//c=100;
        var d=a+b;//d=100+78=178
        b=c+d;//b=100+178=278
        console.log(a);//100
        console.log(b);//278
        console.log(c);//100
        console.log(d);//178
    </script>
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